Oneself

Generic Function

Oneself is a way to build generic functions: functions that take this as the first parameter.

So instead of writing:

Array.prototype.slice(arguments, 1);

you can create a generic function:

var slice = oneself(Array.prototype.slice);
...
slice(arguments, 1)

As a convenenience, oneself provides all Array methods as generic functions under oneself.array, along with functions in string, date, regexp and object.

var slice = oneself.array.slice;
...
slice(arguments, 1)

var map = oneself.array.map,
    getFullYear = oneself.date.getFullYear;
listEqual(
  map([new Date(2011, 3, 15), new Date(2012, 5, 25)], getFullYear),
  [2011, 2012]);

If desired, you can shim Array methods and some implementations already do this.

oneself.array.shim();
oneself.string.shim();

listEqual(
  Array.map(['eB', 'CF'], String.toLowerCase),
  ['eb', 'cf']);

As shown above, generic functions are useful to map methods over collections of objects. oneself also provides placeholder functions that allow you to map methods with specified arguments. This are named the same as the methods, with a _ suffix.

listEqual(
  map([/(.)/, /g$/, /o/, /o$/], oneself.regexp.test_('dog')),
  [true, true, true, false]);

Objects

You can create generic functions from any object.

  function Point(x, y){
    this.x = x;
    this.y = y;
  }

  function point(x, y){
    return new Point(x, y);
  }

  Point.prototype.toString = function(){
    return '('+this.x+', '+this.y+')';
  };

  Point.prototype.describe = function(){
    return 'Point '+this.toString();
  };

  Point.prototype.add = function(x, y){
    return new Point(this.x + x, this.y+y);
  };

  var p1 = point(1,2);


  var describePoint = oneself(Point.prototype.describe);
  equal(describePoint(p1), p1.describe());

As well as placeholder functions:

var add1_1 = oneself(Point.prototype.add)._(1,1);
equals(add1_1(p1), point(2, 3));

Although it might be better to shim your objects. This will create generic functions for all enumerable methods along with toString.

oneself.shim(Point);

listEqual(
  map(map([point(1,2), point(3,4)], Point.add_(10, 20)), Point.toString),
  ['(11, 22)', '(13, 24)']);

(un)curryThis

Making a generic function from a prototype is also called uncurryThis, described here.

uncurryThis is also available under oneself.uncurry and the companion curryThis is called oneself.curry.

curryThis can be used to avoid that = this:

  var x = {
    b: 'hi',
    c: function(w){
      return this.b+' '+w+'!';
    },
    a: oneself.curry(function(self, cb){
      setTimeout(function(){
        cb(self.b);
      }, 100);
    })
  };

  x.a(function(b){});